linux-kernel - Re: [PATCH] APEI/ERST: Fix error message formatting

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Message-ID: <51FA341A.7060307@linux.vnet.ibm.com>
Date:	Thu, 01 Aug 2013 15:40:34 +0530
From:	"Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To:	Bjorn Helgaas <bhelgaas@...gle.com>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>
CC:	Joe Perches <joe@...ches.com>, Borislav Petkov <bp@...en8.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Borislav Petkov <bp@...e.de>,
	Anton Vorontsov <anton@...msg.org>,
	Colin Cross <ccross@...roid.com>,
	Kees Cook <keescook@...omium.org>,
	Tony Luck <tony.luck@...el.com>, Len Brown <lenb@...nel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	"Huang, Ying" <ying.huang@...el.com>
Subject: Re: [PATCH] APEI/ERST: Fix error message formatting

On 07/31/2013 11:30 PM, Bjorn Helgaas wrote:
> On Wed, Jul 31, 2013 at 3:46 AM, Naveen N. Rao
> <naveen.n.rao@...ux.vnet.ibm.com> wrote:
>
>> My key question was about why we are using a field width of 10 implying a
>> 32-bit value, rather than a field width of 18 as suggested by the data type?
>> This shouldn't truncate the value, but if we are specifying the field width
>> for alignment, seems to me it is better to match the data type.
>
> %pR uses a field width of 10 (two for "0x", eight for the value)
> simply because the majority of resource values fit in 32 bits.  Larger
> values extend the width, so it's not a question of truncating any
> data.  But it's no fun to read memory addresses when most of them have
> eight extra leading zeros (the high 32-bits of a 64-bit value).  I
> think the same applies here; most ACPI table addresses still fit in 32
> bits.
>
> We *do* use a field width of 18 for the e820 table, even though many
> of those regions fit in 32 bits.  But that's sort of an exception
> because it's a table where addresses above 4GB are pretty common.

Makes sense, thanks for the explanation.

>
> But at the end of the day, I guess I'm just stating my personal
> preferences and yours might be different.

Right - I'd probably prefer just %#llx. But yeah, the currently used 
field width of 10 looks fine too.


Thanks,
Naveen

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